U.S. patent number 6,169,881 [Application Number 09/072,042] was granted by the patent office on 2001-01-02 for method and apparatus for predicting impending service outages for ground-to-satellite terminal in a satellite communication system.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to Richard Lawrence Astrom, Brian Michael Daniel, Alvin William Sheffler.
United States Patent |
6,169,881 |
Astrom , et al. |
January 2, 2001 |
Method and apparatus for predicting impending service outages for
ground-to-satellite terminal in a satellite communication
system
Abstract
A method (1300) and apparatus (300) combines a terminal blockage
profile for a ground-to-satellite terminal with satellite location
and motion data for one or more satellites (12) in a satellite
communication system (10) to predict an impending service outage or
impairment on a real-time or near real-time basis and reports such
impending outages or impairments, and the expected duration
thereof, to the terminal operator. The prediction of an impending
outage or impairment also can include analysis of information
concerning atmospheric conditions in the vicinity of the terminal
location as well as other potential sources of a service outage or
impairment.
Inventors: |
Astrom; Richard Lawrence
(Gilbert, AZ), Daniel; Brian Michael (Phoenix, AZ),
Sheffler; Alvin William (Mesa, AZ) |
Assignee: |
Motorola, Inc. (Schaumburg,
IL)
|
Family
ID: |
22105203 |
Appl.
No.: |
09/072,042 |
Filed: |
May 4, 1998 |
Current U.S.
Class: |
455/12.1;
455/430; 455/505; 455/67.16; 455/67.7 |
Current CPC
Class: |
H04B
7/18519 (20130101) |
Current International
Class: |
H04B
7/185 (20060101); H04B 007/185 (); H04B 017/00 ();
H04Q 007/20 () |
Field of
Search: |
;455/12.1,13.1,504,505,506,427,430,10,423,424,425,67.6,67.1 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4896369 |
January 1990 |
Adams, Jr. et al. |
5422813 |
June 1995 |
Schuchman et al. |
5555444 |
September 1996 |
Diekelman et al. |
5710758 |
January 1998 |
Soliman et al. |
5918176 |
June 1999 |
Arrington, Jr. et al. |
5946603 |
August 1999 |
Ibanez-Meier |
6032105 |
February 2000 |
Lee et al. |
|
Other References
Barts, et al., Modeling and Simulation of Mobile Satellite
Propagation, Atennas and Propagation, IEEE Transaction on Atennas
and Propagation, vol. 40, No. 4, Apr. 1992. .
An article entitled "Photogrammetric Mobile Satellite Service
Prediction" by Riza Akturan and Wolfhard J. Vogel from NAPEX 94,
Vancouver, BC Jun. 17, 1994. .
An article entitle, "Path Diversity for LEO Satellite-PCS In The
Urban Environment", by Riza Akturan and Wolfhard J. Vogel, from
EERL-95-12A, Dec. 13, 1995. .
An article entitle, "Image Analysis As A Tool For Satellite-Earth
Propagation Studies", by Riza Akturan, Hsin-Piao Lin and Wolfhard
J. Vogel, Proceedings of NAPEX XX, Jun. 4-6, 1996, Publication
Sentel, 1996, pp. 243-255..
|
Primary Examiner: Trost; William G.
Assistant Examiner: Legree; Tracy M
Attorney, Agent or Firm: Wuamett; Jennifer B. Bogacz; Frank
J.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is related to co-pending application Ser. No.
08/963,490 filed on Nov. 3, 1997 and assigned to the same assignee
as the present application, which application is incorporated
herein by reference. This application also is related to co-pending
application Ser. No. 08/845,487, filed on Apr. 25, 1997 and
assigned to the same assignee as the present application, which
application also is incorporated herein by reference.
Claims
What is claimed is:
1. A method for a ground-to-satellite terminal to predict a service
outage in a satellite communication system, the method comprising
the steps of:
a) receiving a terminal blockage profile based upon a location of
said ground-to-satellite terminal;
b) receiving a satellite blockage profile of one or more satellites
of said satellite communication system;
c) using said terminal blockage profile and said satellite blockage
profile to predict a service outage for said ground-to-satellite
terminal;
d) combining said terminal blockage profile and said satellite
blockage profile to generate a service status display report for
use in predicting said impending service outage or impairment;
and
e) said service status display report comprises a circular operator
display showing one or more satellites located within a
field-of-view of said ground-to-satellite terminal within a
predetermined time interval and showing one or more obstructed
region where a communications link between said ground-to-satellite
terminal and said one or more satellites may be blocked or
otherwise impaired during said predetermined time interval, and
wherein said circular operator display is generated, at least in
part, from an optical image corresponding, at least in part, to a
field-of-view of said antenna of said ground-to-satellite
terminal.
2. The method of claim 1, wherein the step of receiving a terminal
blockage profile comprises the step of creating the terminal
blockage profile, including the steps of:
(a1) gathering, by said ground-to-satellite terminal, blockage data
at a site of an antenna of said ground-to-satellite terminal;
and
(a2) mapping said blockage data to a blockage profile database.
3. The method of claim 2, wherein step (a1) further includes the
step of gathering Fresnel zone signal data from one or more
line-of-sight communication link signals.
4. The method of claim 2, wherein step (a1) further includes the
step of measuring data describing a field-of-view of the antenna of
the terminal wherein the measurements can be taken anywhere along a
spectrum.
5. The method of claim 2, wherein step (a1) further includes the
step of forming a backscatter representation of a field-of-view of
the terminal antenna.
6. The method of claim 1, wherein step (b) comprises the step of
creating a satellite blockage profile of one or more satellites
including the steps of:
(b1) monitoring a beacon signal transmitted by the terminal;
and
(b2) storing beacon signal measurements describing a relative
strength of the beacon signal into a database.
7. The method as claimed in claim 1, wherein said service status
display report comprises a rectangular operator display showing one
or more satellites located within a field-of-view of said
ground-to-satellite terminal within a predetermined time interval
and showing one or more obstructed region where a communications
link between said ground-to-satellite terminal and said one or more
satellites may be blocked or otherwise impaired during said
predetermined time interval, and wherein said rectangular operator
display is generated, at least in part, from rectangular
coordinates corresponding to said terminal blockage profile.
8. The method of claim 1, wherein step (c) comprises the steps
of:
(c1) determining, for a particular time increment, whether at least
one satellite is in clear view of an antenna associated with said
ground-to-satellite terminal;
(c2) recording a result of step (c1);
(c3) repeating steps (c1)-(c2) over a predetermined time interval;
and
(c4) using recorded results to create a service outage time line
profile.
9. The method as claimed in claim 8, further including the step
of:
(c5) storing a record corresponding to said service outage time
line profile.
10. The method as claimed in claim 9, further including the step
of:
(c6) using said record corresponding to said service outage time
line profile to verify a service outage claim.
11. The method as claimed in claim 9, further including the step
of:
(c6) using said record corresponding to said service outage time
line profile to aid in trouble-shooting and providing maintenance
service for said ground-to-satellite terminal.
12. The method as claimed in claim 9, further including the step
of:
(c6) periodically updating said service outage time line
profile.
13. The method as claimed in claim 1, further comprising the step
of:
(d) using said terminal blockage profile to generate an impending
service outage notice for warning a terminal operator of said
impending service outage or impairment.
14. The method of claim 1, further including the steps of:
d) receiving signal strength data; and
e) using said signal strength data to predict a service impairment
due to an atmospheric condition.
Description
FIELD OF THE INVENTION
This invention relates generally to the field of wireless
communications, and more particularly to predicting impending
service outages for a ground-to-satellite terminal in a satellite
communication system.
BACKGROUND OF THE INVENTION
The frequency allocations for wireless communication networks
employing non-geosynchronous satellite communications normally
reside in the UHF-, L-, S-, and K-Band frequencies or higher.
Wireless communication systems utilizing K-Band frequencies require
a clear line-of-sight between each node of the communication
network for high-quality communications. Objects such as trees,
utility poles, mountains, buildings, and overpasses that lie along
the communications path will effectively fade or block the
communication transmissions at K-Band frequencies and higher,
therefore degrading, interrupting, or terminating the communication
path.
Furthermore, for a ground-to-satellite radio communication link
that utilizes low-earth orbiting satellites which move across the
sky and rise and set at the horizon, the percentage of time that
the communication link is available varies considerably depending
upon the buildings, trees and other blocking items in the vicinity
of the ground antenna. Likewise, occurrence of service outages for
an operator of a particular terminal can vary over time as a result
of changes in the vicinity of the ground antenna (e.g., due to
maturation of trees and/or construction of new buildings,
atmospheric conditions, and the like). Customers of these systems,
however, are typically not informed as to when their communication
link may be blocked due to such obstacles or as a result of
atmospheric conditions, such as rain for example.
Therefore, what is needed is a system and a method which provides
an advanced warning on a real-time or near real-time basis of
impending periods of service outages or degradation of service
quality resulting from obstacles or impairment of communication
links to allow customers to prepare for and plan around such
impending outages. What is also needed is a method and apparatus to
allow service providers to have a record of actual service outages
to verify customer outage claims and to aid in trouble-shooting and
providing maintenance service for customer terminals.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention can be derived by
referring to the detailed description and claims when considered in
connection with the figures, wherein like reference numbers refer
to similar items throughout the figures, and wherein:
FIG. 1 illustrates a communication system for providing terminal to
satellite communication links in accordance with a preferred
embodiment of the present invention;
FIG. 2 illustrates a time stepped position of a satellite of the
communication system of FIG. 1, a terminal, and a structure
blocking a communications path between the satellite and the
terminal in accordance with a preferred embodiment of the present
invention;
FIG. 3 illustrates a block diagram of an apparatus for predicting
impending service outages or impairments in an individual
ground-to-satellite terminal and reporting such impending outages
or impairments to a terminal operator in accordance with a
preferred embodiment of the present invention;
FIG. 4 illustrates a representation of a field-of-view of a
terminal illustrating potential signal obstructions in accordance
with a preferred embodiment of the present invention;
FIG. 5 illustrates a flow chart of a method of establishing and
responding to a blockage environment in a communication system in
accordance with a preferred embodiment of the present
invention;
FIG. 6 illustrates a flow chart of a method of creating a terminal
blockage profile based on Fresnel diffracted signals in accordance
with a preferred embodiment of the present invention;
FIG. 7 illustrates a graphical diagram based on Fresnel diffracted
signals for a field-of-view of a terminal derived in accordance
with a preferred embodiment of the present invention;
FIG. 8 illustrates a flow chart of a method of creating an optical
terminal blockage profile in accordance with a preferred embodiment
of the present invention;
FIG. 9 illustrates an optical terminal blockage profile of a
field-of-view of a terminal derived in accordance with a preferred
embodiment of the present invention;
FIG. 10 illustrates a flow chart of a method of creating a
backscatter terminal blockage profile in accordance with a
preferred embodiment of the present invention;
FIG. 11 illustrates a backscatter terminal blockage profile of a
field-of-view of a terminal derived in accordance with a preferred
embodiment of the present invention;
FIG. 12 illustrates a flow chart of a method of creating a
satellite blockage profile in accordance with a preferred
embodiment of the present invention;
FIG. 13 illustrates a flow chart of a method for predicting
impending service outages or impairments in an individual
ground-to-satellite terminal and reporting such outages or
impairments to a terminal operator in accordance with a preferred
embodiment of the present invention;
FIG. 14 illustrates a service outage time line profile in
accordance with a preferred embodiment of the present
invention;
FIG. 15 illustrates a service status tracking display for use in a
terminal operator display for predicting the initiation and
duration of a service outage in accordance with a preferred
embodiment of the present invention;
FIG. 16 illustrates a service status tracking display for use in a
terminal operator display for predicting the initiation and
duration of a service outage in accordance with an alternate
embodiment of the present invention;
FIG. 17 illustrates a terminal operator display in accordance with
a preferred embodiment of the present invention; and
FIG. 18 illustrates a simplified block diagram of a user terminal
in accordance with a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The present invention provides, among other things, a method and
apparatus which combines a sky blockage map for an individual
ground-to-satellite terminal in a satellite communication system
with information concerning the direction and location of system
satellites above a minimum elevation angle to predict impending
service outages or impairments for an individual
ground-to-satellite terminal in a satellite communication system
and to notify the terminal operator of such impending outages or
impairments, and the expected duration of the same. The present
invention can be used to predict and notify a terminal operator of
impending outages or impairments of virtually any type, including,
for example outages or impairments resulting from buildings, trees,
weather or atmospheric conditions, and even spectrum sharing or
interference mitigation issues. In a preferred embodiment of the
present invention, impending service outages are predicted on a
real-time or near real-time basis, and the terminal operator is
informed as to when the communication link will be reacquired and
service will resume.
By employing the method and apparatus of the present invention to
predict service outages or impairments and report impending outages
or impairments to the terminal operator, the operator will be
warned of impending outages or impairments. Providing such warnings
to users minimizes user frustration in the event of an outage and
allows a terminal operator to have a more realistic expectation of
the quality of service capable of being delivered to the operator.
Moreover, providing such warnings also allows the operator to take
appropriate precautions to minimize effects of interruption of
service, such as unexpected interruption of transmission or receipt
of data or information.
The present invention also provides a method and apparatus which
allows service providers to access records of service outages or
impairments experienced by their customers or subscribers to verify
customer outage claims and to aid in trouble-shooting and providing
maintenance service for customer terminals.
Wireless communication systems which operate at relatively high
operating frequencies such as K-Band frequencies or higher, require
unobstructed lines-of-sight between the nodes of the communication
system to maintain high-quality communication pathways or links. If
one or more obstructions partially or completely block a
line-of-sight between the nodes, degradation, interruption, and/or
termination of a communication pathway or link can result.
Non-geosynchronous satellite-based communication systems normally
incorporate broadband services utilizing relatively high frequency
allocations in communication links between one or more
non-geosynchronous satellites and terminals based below, near, or
above the surface of the earth. Non-geosynchronous satellites
continuously move about the earth in predetermined orbital
traverses. Therefore, in non-geosynchronous satellite-based
communication systems, the quality of the communication pathways or
links necessarily depends on the ability of the communication
system to maintain the communication links in the presence of
potential blocking, fading, interference and other factors that can
severely affect communication pathways or links. Thus, unobstructed
direct lines-of-sight between terminals and satellites are
necessary to maintain the communication pathways at an adequate
level of service.
With regard to earth-based or ground-based terminals, the motion of
non-geosynchronous satellites with respect to the ground ultimately
presents problems when one or more of the satellites reside at
sufficiently low elevation angles relative to the terminals because
of the line-of-sight blockage that ultimately occurs as a result of
trees, buildings, mountains, and the like between the terminals and
the satellites. Thus, to maintain the communication pathways or
links, it is necessary to switch or hand-off the communication link
or links from the obstructed satellite to another satellite in
clear line-of-sight of the terminal. Although current algorithms
are designed to switch or hand-off from a satellite which is about
to drop below a minimum elevation angle to a new one which is
higher than the minimum elevation angle with respect to the
terminal, the present invention has the capability to respond to
the localized environmental obstructions around the terminal in
order to maintain one or more communication links and to inhibit
fading and blocking of one or more communication links. The present
invention also has the capability of predicting when communication
links may, nonetheless, temporarily be inhibited as a result of an
environmental obstruction and of informing the terminal operator of
an impending temporary service outage or impairment.
It is contemplated that communication terminals include those that
could be either continuously or intermittently mobile or positioned
in a permanent location such as on the roof of a user's
building/house. Terminals could be individual ground-based customer
premise units or a primary communication system control facility.
It is also contemplated that terminals could be located anywhere
below, near, or above the surface of the earth when suitable and
practical.
In this regard, the field-of-view of a selected terminal at any
location normally suffers from varying elevations of obstructions
that can degrade, interrupt, and/or terminate communication links
between the terminal and one or more of the non-geosynchronous
satellites located at low elevation angles. The present invention
increases the efficiency and economy of non-geosynchronous
satellite-based communication systems utilizing relatively
high-band frequencies and minimizes degradation, interruption, and
termination of one or more of the communication links as a result
of local environmental obstructions that can compromise the
line-of-sight between terminals and satellites. The present
invention is not only advantageous in combination with K-Bands and
other higher frequency bands, but also any frequency band that is
prone to fade and blockage as a result of obstructions or
interference.
Referring to FIG. 1, communication system 10 for facilitating one
or more terminal-satellite communication links is shown. Reference
communication elements of communication system 10 are represented
by satellite 12 and terminal 16 (located within or near the
represented structure). Satellite 12, also referred to as a node,
transmits and maintains communication pathway or link 15 with a
terminal 16 having an antenna 19 or other mechanism suitable for
maintaining a communication link with one or more satellites 12.
With reference to FIG. 1, satellite 12 is non-geosynchronous in
relation to antenna 19. In alternate embodiments of the present
invention, system nodes could be devices other than satellites 12.
For example, a node could be a ground-based or aircraft-mounted
transceiver. In addition, some of the advantages of the present
invention could be realized where the node is stationary.
Consistent with the foregoing discussion, terminal 16 and/or
antenna 19 could be positioned below, near, or above the surface of
the earth. In addition, terminal 16 and/or antenna 19 could be
mobile, movable from one location to another, or positioned in a
permanent location. However, to facilitate ease of discussion,
terminal 16 is a terrestrial ground-based terminal located at a
selected position upon the surface of the earth. Communication
system 10 desirably operates at relatively high operating
frequencies such as K-Band frequencies or higher. As a result,
unobstructed lines-of-sight are desirable or required between one
or more satellites 12 and antenna 19 to maintain one or more
communication pathways or links 15.
To illustrate the anomaly and environment of fading and blocking,
attention is directed to FIG. 2. In FIG. 2, illustrated is a time
stepped position of a satellite 13 of communication system 10. Also
shown is terminal 16 and communication link 18 maintained by and
between satellite 13 and antenna 19 of terminal 16. A structure 20
is further shown positioned intermediate antenna 19 and satellite
13 when satellite 13 is in position 26. Arrowed line 14 indicates a
flight path of satellite 13 along a predetermined orbital traverse.
Satellite 13 is shown as it might appear at two different
positions, position 25 and position 26, at two different instances
along its flight path. Position 25 of satellite 13 is somewhat more
elevated relative to antenna 19 than position 26. In position 25,
the line-of-sight and communication link 15 between satellite 13
and antenna 19 are completely unobstructed. However, in position
26, the line-of-sight and communication link 18 between satellite
13 and antenna 19 are obstructed by structure 20 which could result
in either the degradation, interruption, or termination of
communication link 18.
Consistent with the foregoing discussion, and like other
ground-based terminals, antenna 19 could be present in rural,
suburban, or urban areas. At any of these locations, antenna 19
could have a user sky field-of-view having varying degrees of
localized signal obstructions such as trees, shrubs, utility poles,
small and large buildings, bridges and the like above which the
user sky is unobstructed and below which the user sky is partially
or totally obstructed. At any location at which antenna 19 resides,
the localized signal obstructions define a localized fade and
blockage environment.
Regarding fading and blocking, each are greatly dependent upon the
nature of the environmental obstructions. For instance,
communication pathways normally experience shadowing when the
line-of-sight between the satellite and the terminal is obstructed
by trees and shrubs whereby K-Band signals are typically completely
blocked by trees, or the like. In this regard, the degree of
shadowing, or partial blockage, is greatly dependent upon the
frequency of the carrier and the amount of foliage present upon the
trees and bushes and other similar plant growth. Although shadowing
does not necessarily block a communication pathway, its presence
greatly diminishes the quality of the communication pathway and can
lead to the eventual termination of the communication pathway. On
the other hand, communication pathways normally experience complete
blockage when the line-of-sight between the satellite and the
terminal is obstructed by mountains and structures such as
buildings or overpasses. In these cases, the line-of-sight becomes
completely obstructed, often resulting in the termination of the
communication pathway.
To accommodate local environmental obstructions and to increase the
economy, efficiency, and reliability of communication system
resources, the method and apparatus of the present invention
operate to ascertain the blockage environment or the nature of
local environmental obstructions present within the field-of-view
of the terminal in order to establish where the user sky is clear,
where it is shadowed by trees or shrubbery, and where it is blocked
as a result of mountains and structures such as buildings or
overpasses to accurately and reliably predict impending outages or
impairments of a communication pathway or link between an
individual ground-to-satellite terminal and one or more satellites
of a satellite communication system. A user blockage map is then
created and merged with a satellite sky path profile to create a
satellite blockage profile. This profile is then used to construct
an outage time line profile for the ground-to-satellite terminal
and to predict and communicate or report impending service outages
or impairments to the terminal operator, as discussed in further
detail below.
FIG. 3 illustrates a block diagram of an apparatus 300 for
predicting service outages or blockage in an individual
ground-to-satellite terminal and reporting such outages or
impairments to a terminal operator in accordance with a preferred
embodiment of the present invention. In a preferred embodiment of
the present invention, apparatus 300 predicts and reports impending
service outages or impairments to a terminal operator on a
real-time or near real-time basis.
Apparatus 300 includes fisheye lens camera 350 having a
hemispherical fisheye lens that is typically on a telescoping pole
long enough to reach the peak of a roof to where the antenna of the
terminal is to be placed. The camera may be stabilized horizontally
and north may be identified on the resulting image.
FIG. 4 illustrates a terminal field-of-view 50 taken by a fisheye
lens camera, such as fisheye lens camera 350 (FIG. 3), at the site
of a ground-to-satellite terminal antenna, such as antenna 19(FIG.
2) and illustrates potential signal environment obstructions.
Field-of-view 50 illustrates obstructions 52 present at low
elevation angles which may lead to fading and blocking. Although
obstructions 52 are herein shown as trees and shrubs and the like,
obstructions 52 could also include mountains, buildings or other
obstructions. Alternatively, obstructions 52 could represent
atmospheric conditions such as, for example, rain cells or the like
which impair the communication pathway or link between antenna 19
and one or more satellites. Obstructions 52 bound a clear and
unobstructed users sky 53. Field-of-view 50 essentially defines the
blockage profile at the antenna of the terminal at the site, e.g.,
at antenna 19 (FIG. 2) of terminal 16, for example.
Referring back to FIG. 3, the output of camera 350 desirably is a
fisheye image, similar to the one shown in FIG. 4, that is input to
optical processor 352 for creating a blockage map of the sky at the
user terminal site. An example of such a blockage map created by
processor 352 is illustrated in FIG. 9 and will be described in
detail hereinafter. The blockage map of the sky typically includes
digital values representing block/shadowed/clear for each pixel of
the image. It is understood that camera 350 and optical processor
352 may take the form of a laser range finder which does not take
an image, but directly generates sky blockage data typically in
rectangular form.
Apparatus 300 also includes data base 354 which includes the
pointing angles, both azimuth and elevation, to all visible system
satellites as a function of time, for a time period calculated to
be a large enough sample to represent all times. Data base 354 can
be created using methods known to those of ordinary skill in the
art.
Service outage predictor unit 355 combines the sky blockage map
from processor 352, with the satellite pointing angles from
database 354, to determine impending outages or impairments for the
location of the terminal where the photo was taken. The output of
service outage predictor unit 355 desirably is a report sent to
operator display unit 359 displaying status of system satellites
with respect to the terminal on a periodic or continual basis
and/or reporting impending blockages or impairments of the
communication link from antenna 19 (at which the fisheye lens
camera photo was taken) to one or more satellites of the satellite
communication system on a real-time or near real-time basis. In a
preferred embodiment, service outage predictor unit 355 implements
processing steps described in detail with respect to FIG. 13
below.
Apparatus 300 also desirably (but not necessarily) includes signal
strength monitor 357 which is adapted to predict impending system
impairments resulting from atmospheric conditions. In a preferred
embodiment, signal strength monitor 357 is adapted to continuously
monitor broadcast channels from satellites in view of antenna 19
(FIG. 2). This allows the ground-to-satellite terminal to switch to
a different satellite when a blockage occurs or when a satellite
goes over the horizon. The signal strength of a broadcast channel
along with the satellite ephemeris data and the terminal blockage
map can be used to define an atmospheric disturbance such as rain
cells or very dense cloud formations.
The signal strength of a broadcast channel from an unobstructed
view of a second or third satellite is predictable. Generally, if
the signal strength varies from a predetermined profile it is
indicative of an atmospheric condition. Monitoring the signal
strength of the broadcast channels results in a short term
atmospheric map or rain map. The size of the rain/cloud cell can
then be mapped and used to predict the length of an impending
outage or impairment associated with the atmospheric condition.
Referring now to FIG. 5, there is illustrated a flow chart of a
method of establishing and responding to a blockage environment in
a communication system to accurately and reliably predict an
individual ground-to-satellite terminal's percentage of successful
communication linkage time to one or more satellites of a satellite
communication system.
The method begins, in the first instance, by selecting a site in
task 41 at which antenna 19 will reside and then installing antenna
19 in task 42 at a either a rural, suburban, or urban area. After
the site has been selected and antenna 19 installed, a task 46 is
performed to gather fade and blockage data present within the
field-of-view 50 (FIG. 4) of the terminal antenna 19. This task may
be performed by camera 350 (of FIG. 3), for example. For clarity,
fade and blockage data is essentially comprised of the physical
environment of the terminal antenna field-of-view 50 and of
obstructions 52 shadowing or blocking user sky 53. In one
embodiment, fade and blockage data could be simply depicted as a
binary condition, where, for a particular point in the terminal
field-of-view, a zero could represent a clear condition and a one
could represent a blocked condition, for example. In other
embodiments, fade and blockage data could indicate a relative
degree of blocking. For example, a scale of one to ten could be
used to indicate how shadowed a signal is at a particular point.
For example, a zero could indicate that no shadowing exists along
the line of sight. A three could indicate that a mild obstruction
(e.g., a tree) exists along the line of sight. A ten could indicate
a complete blockage condition. This binary or relative degree
depiction of a blockage environment could be applied to both a
terminal blockage profile and a satellite blockage profile, both of
which will be described in detail below.
As will be described in conjunction with FIGS. 6-11, task 46 could
be performed in a variety of ways suitable for allowing a user to
easily and efficiently establish a terminal blockage profile. Four
exemplary ways of gathering fade and blockage data are: (1) using
field-of-view (e.g., optical) data (FIG. 8) such as via fisheye
lens camera 350; (2) using the signature of the signals due to
blocking (FIG. 6) (e.g., Fresnel diffracted signal measurements);
(3) using backscatter signal data (FIG. 10); and (4) using a
directional laser range finder. Preferred embodiments of three of
these ways of gathering fade and blockage data will now be
described, although other ways of gathering fade and blockage data
also could be used.
Referring back to FIG. 5, task 46 may be performed by creating a
terminal blockage profile of a field-of-view of the terminal
antenna. In a preferred embodiment, a terminal blockage profile of
a field-of-view of the terminal antenna is derived from optical
data. However, in alternate embodiments, the field-of-view of the
terminal antenna could be derived from data measurements anywhere
along the spectrum (e.g., optical, infrared, ultraviolet). FIG. 8
is a flow chart of a method of creating an optical terminal
blockage profile in accordance with a preferred embodiment of the
present invention. In this regard, the optical terminal blockage
profile corresponding to field-of-view 50 is initiated in task 92
by first forming an optical image or representation of
field-of-view 50 of the terminal antenna with a fisheye lens camera
(such as camera 350 of FIG. 3) having a full 180 degrees
field-of-view.
The reduction of a fisheye optical image of a selected
field-of-view is described in Akturan & Vogel, Photogrammetric
Mobile Satellite Service Prediction, NAPEX 94 (Jun. 17, 1994). The
optical image, of which would be generally representative to
field-of-view 50 shown in FIG. 4, is then translated and mapped or
plotted via an algorithm or other means in task 94 in the form of a
sky blockage map 96 as evidenced in FIG. 9.
FIG. 9 illustrates an exemplary optical terminal blockage profile
of a field-of-view of a terminal derived in accordance with a
preferred embodiment of the present invention. Sky blockage map 96
corresponds to a two dimensional blockage profile 98 of an optical
representation of field-of-view 50 of antenna 19 plotted in the
form of elevation angle 100 as a function of azimuth angle 102 with
area 104 above curve 105 corresponding to unobstructed user sky 53
in which communication may take place, and area 106 below curve 105
corresponding to a blockage region defined by obstructions 52
present within field-of-view 50 in which communication may not take
place. Map 96 represents a typical output of optical processor 352
of FIG. 3.
Referring back to FIG. 8, once plotted, calibration of sky blockage
map 96 takes place in task 110. In a preferred embodiment,
calibration of map 96 involves determining the direction of zero
degrees in azimuth via a compass or other suitable mechanism to
establish a coordinate system for antenna 19. Completion of tasks
92-110 result in the creation of an optical terminal blockage
profile.
Additionally, referring back to FIG. 5, task 46 could be performed
by creating a terminal blockage profile based on Fresnel diffracted
signals. FIG. 6 is a flow chart of a method of creating a terminal
blockage profile based on Fresnel diffracted signals in accordance
with a preferred embodiment of the present invention. In alternate
embodiments, other methods can be used which indicate blockages
from signal measurements.
In a terminal-satellite communication system utilizing broadband
channels, when the line of sight between the satellite and the
terminal is unobstructed, the signal strength of the communication
link is nearly constant. However, as the satellite moves in the
user sky in relation to the terminal and the line-of-sight is about
to be shadowed or blocked by an approaching obstruction, the
Fresnel diffracted signal strength fluctuates as evidenced by rapid
variations in the diffracted signal's amplitude. The variance in
the amplitude of the Fresnel diffracted signal indicates that
shadowing or blockage is about to occur as a result of an
approaching obstruction.
Large objects such as mountains, buildings, and similar structures
result in large variations in the Fresnel diffracted signal
amplitude. In any event, the signature of the Fresnel diffracted
signal will exhibit certain strength characteristics evidenced by
variances in the Fresnel diffracted signal amplitude depending upon
whether the line-of-sight between the satellite and the terminal is
unobstructed, about to experience partial or total obstruction,
shadowed, partially obstructed, or totally obstructed.
Referring to FIG. 6 and pursuant to the foregoing, Fresnel
diffracted signal data from one or more communication pathways or
links is monitored over a sliding time window in task 64. The
Fresnel diffracted signal data could be monitored either at antenna
19 or at one or more of the satellites 12 of the constellation of
satellites. The Fresnel diffracted signal data is recorded in task
66 either at antenna 19 or at one or more of the satellites 12. The
variations in the signal strength or amplitude of the Fresnel
diffracted signal is then averaged or normalized in task 68 to
create a Fresnel diffracted signal threshold or signature. In a
preferred embodiment, the Fresnel threshold corresponds to an
average signature of Fresnel diffracted signals for an average
communication pathway within the field-of-view 50 of antenna 19. In
alternate embodiments, the Fresnel threshold could be set at a
different level. The Fresnel threshold is then mapped or plotted to
a database in task 70 in the form of a map. Completion of tasks
64-70 results in the creation of a terminal blockage profile based
on Fresnel diffracted signals.
FIG. 7 illustrates a pictorial diagram based on Fresnel diffracted
signals which shows a Fresnel threshold for a field-of-view of a
terminal derived in accordance with a preferred embodiment of the
present invention. Graph 72 corresponds to a two dimensional
profile 74 of a Fresnel signature 76 (e.g., of field-of-view 50 of
antenna 19) plotted in the form of normalized signal intensity or
strength 78 as a function of obstruction clearance 80. FIG. 7
illustrates the amplitude variations of a Fresnel diffracted signal
where the obstruction is relatively straight. The edge of such an
obstruction would be located where the obstruction clearance 80
equals zero at point 81. The variance in the amplitude of the
Fresnel signature 76 corresponds to the blockage environment at the
terminal antenna.
Referring back to FIG. 5, task 46 could further be performed by
creating a backscatter terminal blockage profile by virtue of a
backscatter technique. FIG. 10 is a flow chart of a method of
creating a backscatter terminal blockage profile in accordance with
a preferred embodiment of the present invention. In this regard,
the backscatter terminal blockage profile (e.g., corresponding to
field-of-view 50) is carried out in task 122 by first transmitting
a signal from antenna 19 in each direction (azimuth and elevation)
of interest. The signal could be produced from a transmitter housed
at the site of antenna 19 and could be emitted via antenna 19 or a
similar mechanism in the form of a radio frequency signal, an
infrared signal, or perhaps an ultrasound signal.
Regarding a preferred embodiment, the emitted signal is preferably
a high-frequency (e.g., Ka-band or above) signal, or an infrared
laser, that will reflect off of the environmental obstructions
within field-of-view 50 of the terminal antenna. After transmission
of the signal from antenna 19, the signal will impact obstructions
52 and reflect back to terminal 16 in the form of backscatter
signal data. The backscatter signal data is then detected by
terminal 16 in task 126 and measured in task 128 much like
conventional radar measurements. The measurements are then recorded
in task 130 either at terminal 16 or one or more of the satellites
12. In this manner, antenna 19 could be equipped with detection
capabilities for detecting the backscatter signal data. The
recorded backscatter signal data, which would be generally
representative of field-of-view 50 shown in FIG. 4, is then
translated and mapped or plotted via an algorithm or other means in
task 132 in the form of a map 140 as evidenced in FIG. 11.
FIG. 11 is an exemplary backscatter terminal blockage profile of a
field-of-view of a terminal derived in accordance with a preferred
embodiment of the present invention. Having similar characteristics
to map 96 (FIG. 9) previously discussed, map 140 corresponds to a
two dimensional blockage profile 142 of a backscatter
representation of field-of-view 50 of antenna 19 plotted in the
form of elevation angle 144 as a function of azimuth angle 146.
Area 148 above curve 150 corresponds to unobstructed user sky 53 in
which communication may take place and area 152 below curve 150
corresponds to a blockage region defined by obstructions 52 present
within field-of-view 50.
Referring back to FIG. 5, after and/or concurrent with gathering
fade and blockage data in task 46, a task 158 is performed which
uses the fade and blockage data to create a terminal blockage
profile (e.g., maps 72, 96, 140) of the field-of-view of the
terminal antenna to establish where the user sky about antenna 19
is clear, shadowed, or blocked.
After the terminal blockage profile of the field-of-view 50 of the
terminal antenna has been formed (e.g., by virtue of field-of-view
measurements, Fresnel diffracted signal measurements, or
backscatter measurements), the terminal blockage profile is then
stored in task 160 for eventual use by service outage predictor
unit 355 (FIG. 3). The terminal blockage profile could be stored
either at terminal 16, a separate control facility, or one or more
of the satellites 12 of the constellation.
It may be periodically necessary to update the terminal blockage
profile because the local environmental obstructions at the site at
which antenna 19 resides could change. Additionally, the terminal
blockage profile could require continuous or frequent updating if
the terminal is continuously or intermittently mobile. Updating the
terminal blockage profile would necessarily involve selectively and
periodically or aperiodically repeating, in relevant part, the
foregoing method steps relating to the creation of the terminal
blockage profile.
In furtherance of a preferred embodiment of the present invention,
it is advantageous to determine satellite blockage profiles for use
in predicting and reporting impending service outages or
impairments to a terminal operator in accordance with a preferred
embodiment of the present invention. A satellite blockage profile
maps blockage conditions between a terminal and a satellite from
the satellite's perspective, whereas a terminal blockage profile
maps the blockage environment from the terminal's perspective.
Formation of a satellite blockage profile can be performed in
several ways and takes place in task 163. FIG. 12 describes
formation of a satellite blockage profile in accordance with a
preferred embodiment of the present invention.
FIG. 12 illustrates a flow chart of a method of creating a
satellite blockage profile in accordance with a preferred
embodiment of the present invention. The method described in
conjunction with FIG. 12 does not need to use terminal blockage
profile data derived in accordance with steps 46-160 of FIG. 5.
Rather, antenna 19 desirably is equipped with a beacon (e.g., an
infrared transmitter) that emits a beacon signal which can be
received by a satellite 12. During the course of a satellite pass
(e.g., when satellite 12 is above a minimum elevation angle with
respect to antenna 19), satellite 12 monitors this beacon signal in
step 180 to determine the beacon's relative received strength.
Where the received beacon signal is weak or non-existent, a partial
or total obstruction between the satellite and terminal is likely.
In another alternate embodiment, satellite 12 could be equipped
with a beacon (rather than or in addition to terminal 16) and the
beacon signals emitted by the satellite could be measured at the
ground to determine obstructions.
The relative strengths of the received beacon signal measurements
for a particular terminal are stored in task 182 to a database
located either at terminal 16, a control facility, or one or more
of the satellites 12 of the constellation. Data from numerous
passes over a terminal can be combined to form a terminal blockage
profile in step 183. This profile can be later processed to compute
a map from a satellite's perspective that depicts the trajectory of
the terminal as well as the time evolution of its blocking
environment.
When blockage information is desired for an upcoming satellite pass
with respect to a particular terminal, the satellite orbital path
is predicted, in step 184, by either a satellite, a control
facility, or a terminal. In step 186, at least those portions of
the satellite orbital path for which the satellite will be located
within the field-of-view of the terminal antenna is determined. In
step 188, those portions of the orbital path are analyzed in the
context with the data from the terminal blockage profile derived
from beacon signal measurements.
Based on this analysis, segments of those portions during which a
satellite-to-terminal communication link would be blocked,
shadowed, or clear are determined in step 190. Desirably, this
results in a set of times and/or satellite locations during which
high-quality communications are possible between the satellite and
terminal. In step 192, information describing the blocked,
shadowed, and clear conditions are translated into a satellite
blockage profile for that pass. Thus, performance of steps 180-192
result in the creation of a satellite blockage profile.
In a preferred embodiment, steps 180-182 are repeated each time a
system satellite achieves a minimum angle of elevation with respect
to the terminal, although selectively fewer repetitions could be
performed. Repeated performance of steps 180-182 results in the
creation of a cumulative database of blockage information. Steps
184-192 are performed each time a blockage profile for a particular
satellite pass is desired.
As stated previously, to create a satellite blockage profile in
accordance with FIG. 12, terminal blockage profile data derived
from measurements made by the terminal is not necessary. Therefore,
steps 46-160 of FIG. 5 need not necessarily be performed in order
to achieve the advantages of the present invention.
Referring back to FIG. 5, the satellite blockage profile is stored
in step 198 for eventual use by service outage predictor unit 355
(FIG. 3). Desirably, the satellite blockage profile is stored at
terminal 16, although the profile could be stored in one or more
satellites 12 or a control facility.
FIG. 5 additionally includes step 202 for receiving signal strength
data. Signal strength data desirably is received in the form of a
data from a computer database which is specific for the general
area of the customer location of antenna 19 and represents a
prediction of system availability for non-blocked sky based upon
the weather model and the frequency, broadcast and antenna
characteristics of the system. The output of step 202 is a
prediction of service impairment or outage due to atmospheric
conditions. Signal strength data could be input on a real-time or
near real-time basis, or could be input based on estimates of
weather conditions for some predetermined period of time from a
weather model database. For example, the generation of a weather
model database is described in at least two articles from the
Proceedings of the Twenty-First NASA Propagation Experimenters
Meeting (NAPEX XXI) and the Advanced Communications Technology
Satellite (ACTS) Propagation Studies Miniworkshop held in El
Segundo, Calif. in Jun. 11-13, 1997: (1) a NAPEX XXI article
entitled "A New Rain-Rate Distribution Model: Preliminary Version
for Annual Statistics", by R. K. Crane at the School of Meteorology
at the University of Okla., published on Aug. 1, 1997, and (2) a
NAPEX XXI article entitled "Fade Dynamics and its Evolution: The
Other Part of the ACTS Rain Prediction Model", by Robert M. Manning
of NASA's Space Communication Office, published on Aug. 1, 1997,
the subject matter of which is incorporated by reference
herein.
By virtue of an algorithm or other mechanism present at (1)
terminal 16, (2) one or more of the satellites 12 of the
constellation, or (3) a control facility, a response to the
terminal blockage profile and/or the satellite blockage profile
and/or the signal strength data could be analyzed for potential
effects on the service availability in task 200 to predict
impending service outages or impairments due to environmental
obstacles and/or atmospheric conditions.
FIG. 13 illustrates a flow chart of a method 1300 for predicting
impending service outages or impairments in an individual
ground-to-satellite terminal and reporting such outages or
impairments to a terminal operator in accordance with a preferred
embodiment of the present invention. The steps shown in FIG. 13
desirably are implemented within service outage predictor unit 355
of FIG. 3. Some or all of the steps of method 1300 also can be
executed in a processor included in terminal 16 (FIGS. 1 &
18).
First, in step 410, a sky blockage map such as the one shown in
FIG. 8 is analyzed by a processor, desirably in service outage
predictor unit 355 (FIG. 3). This map may be input, for example,
from optical processor 352 (FIG. 3). In step 412, the database
containing satellite angles is analyzed, for example, from a local
storage device such as database 354 (FIG. 3).
In step 414, a service outage time line profile is constructed
either concurrently or separately from steps 410 and 412. An
example of a service outage time line profile is illustrated in
FIG. 14. Service outage time line profile 500 includes multiple
time increments 510 for a predetermined time interval 520 where
T=T.sub.max, where T.sub.max represents sum of time increments from
T=0 to T=N. Although T.sub.max could be virtually any period of
time represented in seconds, minutes, hours, days, or the like
without departing from the spirit of the present invention, in a
preferred embodiment of the present invention, T.sub.max is set at
1 hour. T.sub.max is incremented by the sampling period, and in a
preferred embodiment, the incremental period is 5 seconds. However,
the aforementioned incremental period is not intended to be
limiting in the present invention, as a plurality of time periods
may be used along with a plurality of time increments with the
basic intent to obtain a plurality of samples that sufficiently
represent the location of satellites with respect to the location
of the terminal.
Time line profile 500 illustrated in FIG. 14 represents a completed
time line profile as it could appear after completing steps 420-429
of method 1300. At step 414, time line profile 500 could appear as
shown, where each time increment 510 has a designation, such as "C"
(clear) or "B" (blocked) for the particular time increment, or time
line profile 500 could be devoid of any designation for time
increments 510.
Referring back to FIG. 13, in step 416, Time (T) is set to zero. In
step 418, at T=0, outage time line profile 500 is initialized such
that each time increment 510 (FIG. 14) is set to a default
designation of "C" (clear) indicating that no impending service
outage is expected for that time increment.
In step 420, a loop process is initiated whereby for T=0 and for
each time increment Time=T+ increment, each satellite of the
satellite constellation is examined from the database and it is
determined whether each satellite is blocked or clear based upon
the sky blockage map. In step 422 a determination is made as to
whether all satellites are blocked for a particular time increment
510 (FIG. 14). If all satellites are blocked for the time increment
currently being examined, then in step 424 the time line profile
entry for that time increment will be changed from the default
entry of "C" (clear) to an entry of "B" (blocked). If, however, in
step 422 a determination is made that all satellites are not
blocked for the particular time increment, no adjustment will be
made to the default entry on the time line profile for that
increment. In step 428 a determination is then made as to whether
the predetermined time interval set on the time line profile has
expired, or in other words, whether T=T.sub.max. If a determination
is made that the time interval has not expired, then the next time
increment will be processed in accordance with step 426 and steps
420-426 will be repeated continually for the remaining time
increments in the predetermined time interval 520. If it is
determined in step 428 that the time interval has expired, then the
method proceeds to step 429 where the outage time line profile is
completed.
FIG. 14 illustrates a completed service outage time line profile in
accordance with a preferred embodiment of the present invention. As
a result of the analyses performed in steps 420-429, each time
increment 510 in service outage time line profile 500 (FIG. 14)
desirably is designated as "B" (blocked) or "C" (clear). In a
preferred embodiment, if one or more satellites are in an
unobstructed line of site of the terminal, then for that increment
of time, the satellite terminal is considered to have a clear view
of the system. In an alternate embodiment, time increments could
receive designations other than or in addition to "C" (clear) and
"B" (blocked). For example, time increments 510 also could be
designated as "impaired" where fading, signal attenuation, or
partial blockage will occur as a result of atmospheric conditions
or partial environmental obstructions. Alternatively, such impaired
increments could simply be designated as blocked.
Additionally, other system rules may be implemented herein such as
the highest satellite must be in clear view in order to invoke a
clear designation for a particular time increment. Alternately, the
rules may require that two or more satellites must be in clear view
in order to invoke a system clear designation for a particular time
increment.
Yet alternatively, the rules may be adapted to designate an
increment as being blocked if during that increment using one or
more otherwise unobstructed communication links to one or more
satellites of the constellation would cause interference with a
satellite of another satellite communication system as a result of
a spectrum sharing arrangement or the like. "Outages" arising from
interference mitigation could simply be identified during a time
increment as a "blockage" or they could be identified in some other
manner so as to enable notification to the terminal operator that
the impending service outage is the result of a spectrum sharing
arrangement rather than a result of system error or environmental
or atmospheric condition. In any event, the result of steps 414-428
is, in step 429, to create a completed outage time line profile,
such as outage time line profile 500 shown in FIG. 14, which
indicates whether the system will be available (clear) or not
available (blocked) during the particular time interval.
In step 430, a service status display is generated. FIG. 15
illustrates an example of a service status display for use in
predicting the initiation and duration of a service outage in
accordance with a preferred embodiment of the present invention.
Service status display 1500 is a computer software generated
operator interface display which desirably is generated by service
outage predictor unit 355 (FIG. 3) and made to appear on operator
display unit 359 (FIG. 3). Service status display 1500 desirably is
generated by combining a terminal blockage map for the individual
ground-to-satellite terminal (step 410 of method 1300, FIG. 13)
with data concerning the current locations and directions of all
system satellites above the minimum elevation angle (step 412 of
method 1300, FIG. 13). The result, in a preferred embodiment of the
present invention, is a circular operator display 1510 showing each
satellite 13, 14 within a 360 degree field-of-view of the
ground-to-satellite terminal within a predetermined time interval.
The direction of travel of satellites 13 and 14 is represented,
respectively, by arrows 1530 and 1540. Circular operator display
1510 also shows obstructed region(s) 1520 where communications
links with satellite could be blocked or otherwise impaired and
clear or unobstructed region/s 1525 where communication links to
satellite are not expected to be blocked or impaired.
For example, at the time increment represented by service status
display 1500, there are two satellites in view: satellite 13, which
is in the west region (270 degrees) of the field-of-view; and
satellite 14, which is in the southeast region (between 090 and 180
degrees) of the field-of-view of the antenna. Although satellite 13
is located within obstructed region 1520, satellite 14, is located
within clear region 1525. Thus, the system is currently
unobstructed or "clear."
Desirably, service status display 1500 is generated and updated on
a continual basis and is available for viewing by the terminal
operator continually. However, in alternate embodiments, service
status display 1500 could be generated on a less frequent basis and
appear only at specified times or could be adapted to appear only
when a service outage or impairment is expected to occur within
some predetermined amount of time or only when the terminal
operator requests status information.
Moreover, circular operator display 1510, is intended to be an
exemplary illustration of a service status display and is not
intended to be limiting of the scope of the present invention.
Service status display 1500 could take on other forms without
departing from the spirit of the present invention. For example,
FIG. 16 illustrates a service status display for use in a terminal
operator display for predicting the initiation and duration of a
service outage in accordance with an alternate embodiment of the
present invention. Rectangular coordinates operator display 1600
illustrates sky blockage data represented in rectangular form
rather than the circular display shown in FIG. 15. Rectangular
coordinates operator display 1600 reports satellite availability,
and in turn impending outages or impairments in a plot of points
generated by plotting elevation angle data on a first axis 1610
against azimuth angle data on a second axis 1615. Obstructed region
1620 corresponds to obstructed region 1520 in FIG. 15, and clear or
unobstructed region 1625 corresponds to clear or unobstructed
region 1525 in FIG. 15. Satellites 13 and 14 are again represented
along with their corresponding directions of travel as represented
by arrows 1530 and 1540 respectively.
Referring back to FIG. 13, after the service status display is
generated in step 430, the next time interval can be processed in
step 434, and steps 416-434 can be performed iteratively. In this
embodiment, service status display 1500 is used by the terminal
operator to identify impending service outages or impairments by
monitoring the direction of travel and position of the satellites
in view with respect to obstructed regions 1520 so that the
terminal operator could prepare for impending outages before they
occur.
Additionally, steps 435 and 436 also can be added to the iterative
process. When steps 435 and 436 are performed, an impending service
outage notice is generated in addition to the service status
display generated in step 430. In step 435, service outage
predictor unit 355 (FIG. 3) examines the service time line outage
profile completed in step 429 and determines whether potential
communication links with all possible available satellites are
blocked at any time during the predetermined time interval. If a
determination is made that all satellites will be blocked at any
time during the predetermined time interval, an impending service
outage notice will be generated and presented to the terminal
operator through the operator terminal display 359 (FIG. 3).
FIG. 17 illustrates a terminal operator display for reporting an
impending service outage in accordance with a preferred embodiment
of the present invention. In FIG. 17, operator terminal display
1700 includes service status display 1500 and impending service
outage notice 1710. Impending outage report 1710 desirably includes
information indicating the predicted onset and duration of an
impending outage report. However, impending outage report 1710 also
could include different types of information in addition to or as a
substitute for such information (e.g., information concerning the
reason for an impending outage or impairment).
Impending service outage notice 1710 desirably is generated as
needed to provide the terminal operator with sufficient warning of
an impending service outage to allow the operator to take
precautions to mitigate the effects of a service outage (e.g.,
execute operations, save or send data, etc.). For example, during
the time interval represented by service status display 1500 in
FIG. 15, the system is currently clear or unblocked. However,
satellite 14 is traveling in a direction of travel 1540 toward
obstructed region 1520 (e.g., satellite 14 is about to travel
behind a small tree in the southeast and will become blocked), and
satellite 13 already is within an obstructed area (e.g., behind a
tree in the west). Thus a service outage is impending. In step 435
of method 1300 (FIG. 13), this impending service outage will be
recognized by service outage predictor unit 355 (FIG. 3) and
reported to the terminal operator through impending service outage
notice 1710 as shown in FIG. 17. The impending outage service
notice could appear concurrent with service status display 1500 or
could appear alone, without the accompanying service status
display.
FIG. 18 is a simplified block diagram of a ground-to-satellite
terminal in accordance with a preferred embodiment of the present
invention. Terminal 220 includes processor 222, memory storage
device 226, and operator display unit 359. Memory storage device
226 is capable of storing a terminal blockage profile as well as a
satellite blockage profile and data relating to atmospheric
conditions, including weather conditions. As described in
conjunction with various embodiments of the invention, the terminal
blockage profile could include, for example, a map of the
environment experienced by the terminal antenna which could be a
map derived from signal measurements (e.g., Fresnel diffracted
signal measurements), a field-of-view map, or a backscatter data
map. In alternate embodiments, a terminal blockage profile could be
stored at a control facility, a satellite, or in other nodes of the
communication system, or a combination thereof.
Additionally, memory storage device 226 desirably is adapted to
store service outage time line profiles and/or impending outage
reports. Such profiles and/or reports can then be accessed by the
system operator or other service provider associated with the
communication system to verify customer outage claims, to provide
objective data concerning service outages, and/or to aid in
trouble-shooting and providing maintenance service for operator
terminals. In a preferred embodiment, the system operator or
service provider can access records concerning outages or
impairments remotely from the system operator or service providers
location through transceiver 227. In an alternate embodiment, the
system operator or service provider can extract such records
directly from the terminal at the terminal's location.
Processor 222 is used to respond to the terminal blockage profile,
when necessary. Such response could be initiated by processor 222,
for example, or could result from the receipt of an instruction
directing processor 222 to respond to the terminal blockage
profile. Responding to the terminal blockage profile, for example,
could involve processor 222 executing an algorithm for initiating
one or more hand-offs to one or more satellites. In a preferred
embodiment, processor 222 is also for periodically initiating and
generating updates of outage time line profiles for the terminal.
Additionally, in a preferred embodiment, processor 222 is adapted
to execute one or more of the steps described with reference to
method 1300 (FIG. 13). Desirably, processor 222 is adapted to carry
out the functions described herein with reference to service outage
predictor unit 355 (FIG. 3). In alternate embodiments, the
functions described with reference to service outage predictor unit
can be carried out at a control facility, in a satellite, or in
other nodes of the communication system, or a combination thereof.
Processor desirably is in communication with operator display unit
359 and/or service outage predictor unit 355, which either can be
collocated as part of processor 222 or can be an independent unit
as shown in FIG. 3.
In a preferred embodiment, terminal 220 also includes measurement
device 224. Measurement device 224 is not necessary in those
embodiments where terminal 220 does not gather data for its
blockage profile. However, in those embodiments where terminal 220
does gather data for the terminal blockage profile, measurement
device 224 could be, for example, a device for detecting Fresnel
diffracted signals, an optical fisheye lens camera, or a
backscatter signal detection device.
In summary, the present invention provides a method and apparatus
which combines the terminal's blockage profile with satellite
location and motion data and also optionally with atmospheric
information in the form of signal strength and/or weather models to
predict impending service outages or impairments on a real-time or
near real-time basis and to report such impending outages or
impairments and the expected duration thereof to the terminal
operator. The service predictor unit could be included temporarily
or permanently in a customer's stationary ground-to-satellite
terminal or even in a moveable terminal. The inclusion of a service
outage predictor unit directly in an operator terminal provides a
direct source of information concerning the performance of the
terminal at the terminal site.
As an application for the present invention, communication systems
using non-geosynchronous satellites may make use of this service
predictor unit to allow customers of such systems to have advanced
warnings of impending service outages. The system operator or other
service provider associated with the communication system can use
the service outage information generated by the method and
apparatus of the present invention to verify customer outage
claims, to provide objective data concerning service outages,
and/or to aid in troubleshooting and providing maintenance service
for operator terminals. Similarly, service outage information
generated by the method and apparatus of the present invention also
can be monitored over time to determine if any degradation in
service is due to growth of foliage or construction of new
buildings in the area of the operator antenna.
The present invention has been described above with reference to a
preferred embodiment. However, those skilled in the art will
recognize that changes and modifications could be made in the
described embodiments without departing from the nature and scope
of the present invention. Various changes and modifications to the
embodiment herein chosen for purposes of illustration will readily
occur to those skilled in the art. To the extent that such
modifications and variations do not depart from the spirit of the
invention, they are intended to be included within the scope
thereof which is assessed only by a fair interpretation of the
following claims.
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